Aquatic and marine biofouling is the attachment of organisms to wetted or submerged man-made surfaces. Specifically, the accumulation of these biofouling organisms poses many significant problems. As one example, accumulation of barnacles or mussels on ship hulls reduces the ship performance by increasing hydrodynamic drag which reduces maneuverability and increases fuel consumption. Another example, the accumulation of zebra mussels leads to clogging of water supply pipes, water intakes, and heat exchangers which restricts water flow in these structures resulting in a reduction or loss of performance for facilities that utilizing the water. As a further example, navigational buoys can sink under the weight of the attached biofouling organisms, and dock pilings and ship hulls can deteriorate faster through the corrosion of steel and concrete. Many treatments have been developed to counteract biofouling which include specialized coatings, including fouling release coatings and biocide-impregnated coatings. But, these above methods have limitations such as bioaccumulation of released toxic antifouling substances or restrictions or limits to their performance.
Insects such as mosquitos, lice, flies, fleas, and ticks are known to be vectors for the transmission of infectious agents such as parasites, viruses, and bacteria. Some of the diseases which can be transmitted by these insects include malaria, Dengue fever, Yellow fever, Zika virus, Chikungunya, Lyme disease, West Nile virus, and others. In some parts of the world, these diseases have become a public health issue. In response, various types of insect repellents have been developed to repel insects from landing and biting a host. Commercial compounds such as DEET (N,N-diethyl-meta-toluamide) have been shown to be effective repellents, and relatively safe when used as directed. However, most people do not use DEET as directed and there is also significant consumer aversion to DEET. Aside from limitations to its application such as avoiding contact with eyes, open skin, and mucosal membranes, there are a number of drawbacks to DEET including that it is structurally similar to toluene and thus dissolves many types of paints, coatings and textiles and there are concerns of resistance because it must be used at concentrations that affect target organism fitness.
Octopamine receptors (OctR) belong to the biogenic amine receptor family which includes receptors for dopamine, serotonin, and tyramine. Octopamine is a major signaling molecule in arthropods, including insects and barnacle cyprids, with neuromodulator, neurotransmitter, and neurohormone functions. Octopamine receptors can be subdivided into at least two different subclasses called alpha-like (α-like) and beta-like (β-like) OctRs. We found that molecules which activate (α-like OctR) would disrupt the biting activities of insects and the settlement activity of barnacle cyprids. In the past, small molecules have been developed to activate the OctRs; however these molecules also activate vertebrate alpha-2 adrenergic receptors (α2AR) homologues meaning that the molecules developed do not readily discriminate between invertebrates OctRs and vertebrate α2ARs. The interaction of these small compounds with vertebrate α2ARs produces sedative, tranquilizing, and muscle relaxation properties. Therefore, it has not been possible to find a highly selective small molecule that is capable of readily discriminating between arthropod OctR and vertebrate α2AR, thereby, deterring the arthropod while not also significantly affecting the host.
What is needed is a deterrent for arthropods and marine organisms which would be considered highly effective yet safe for vertebrates due to its high selectivity for a target invertebrate OctR over the off-target vertebrate α2AR.